Wind turbines in the prior art have largely been designed with rotor blades having the aerodynamic characteristics of wings. Wings have been characterized in the prior art according to their aspect ratio. The aspect ratio is discussed in U.S. Pat. No. 6,264,136, issued on Jul. 24, 2001 to Weston. In the prior art, aspect ratios for wings have been defined perhaps somewhat ambiguously as the ratio of the spanwise length of the wing to the mean chordal length of the wing. Aspect ratios for wings are typically greater than 3:1.
Rotor assemblies of wind turbines in the prior art have typically consisted of airfoiled wings with aspect ratios far exceeding 3:1 and approaching 30:1 and even greater. Disadvantages of this type of wind turbine rotor assembly include self-limiting aerodynamic drag characteristics associated with wings, mechanical stress associated with the very long lever arm of the wing blade, high noise level, and high visual impact.
Also in the prior art, there are aerodynamic structures known as low aspect ratio lifting bodies. Low aspect ratio lifting bodies have been distinguished from higher aspect ratio wings in that lifting bodies have an aspect ratio of less than 2:1, whereas wings have aspect ratios greater than 3:1. Additionally, lifting bodies have been distinguished from wings by certain definite advantageous aerodynamic characteristics in certain applications, which include a higher coefficient of lift at high angles of attack, and generally more favorable drag characteristics, discussed in part in U.S. Pat. No. 2,384,893, issued on Sep. 18, 1945 to Crook.
Also in the prior art, there are wind turbines known as horizontal axis type wind turbines. U.S. Pat. No. 6,064,123, issued on May 16, 2000 to Gislason, describes the general features and operation of horizontal axis wind turbines.